Recently, following the tendency of electronic devices towards becoming smaller and thinner, a mechanical sensor which is used in electronic devices is required to become smaller. As an example of mechanical sensor using stress magnetic effect, a sensor which is already put in practical use is comprised of a cylinder on which an amorphous magnetic alloy thin band having positive saturation magnetostriction constant is adhered and a solenoid coil which detects permeability change in the thin band resulting from applied stress (for example, SAE TECHNICAL PAPER SERIES 920700).
This conventional type of mechanical sensor is provided with a coil produced by winding wires (diameter: more than 20 to 30 .mu.m) in the form of solenoid and a ferromagnetic bulk (thickness: 20 to 30 .mu.m).
However, since the above-mentioned conventional mechanical sensor uses a solenoid wound coil and a ferromagnetic bulk, it is difficult to attain a smaller and more integrated sensor. Furthermore, it is necessary to convert inductance change of the coil into voltage, so that an amplification circuit becomes complicated, compared with converting resistance change into voltage.
An example of plane mechanical sensor which is more suitable for attaining compact size is a distorted gage using a metallic foil, but this sensor has only one thousandth of sensitivity, compared with using stress magnetic effect.